Section 7.3. Future Directions

7.3. Future Directions

At the time of this writing, WS-Policy is at the start of the path toward standardization. The current WS-Policy document focuses on expressing two types of metadata: capabilities (things a service can do) and constraints (things a service requires). One of the next tasks is to gather domain-specific experts and have them specify domain-specific expression languages to express the constraints and capabilities that are relevant for each domain in the form of assertion dialects. Examples of proposals in this area comprise WS-SecurityPolicy, which includes requirements for authentication and message-level security, and WS-ReliableMessaging, which includes capabilities for RM and WS-Transactions (WS-AtomicTransaction and WS-BusinessActivity).

When multiple service assurance protocols exist, it is important for a Web service to be able to indicate which one it supports and what requirements it places on potential requesters.

As Web services gain adoption and more complex Web services applications are deployed, the WS-Policy framework might need to be extended to express and support service agreements (such as WS-Agreements) and specification profiling for interoperability (WS-I conformance claims). Service agreements don't just require a language for expressing goals and objectives. They also need a mechanism for negotiating and associating an agreement with a service endpoint and the parties that are governed by the agreement terms.

It may be necessary to clarify the relationship between WS-Policy and full-fledged semantic description frameworks. Just as WSDL extensions have been proposed to allow semantic expressions to extend the definition of a service interface, individual policy assertions can be annotated with semantic expressions and reasoned about as the semantic Web moves from theory to practice.